It means he’s not very good at communicating his thoughts to you. Lots of guys struggle to do that. It probably also means he’s very frustrated but doesn’t know how to tell you.
You should ask him Sometimes partners ask for space from each other after an argument to let feelings of anger settle before talking again. It usually gives clarity as when you remove the self you can perceive better how you may have handled smth wrong and understand the other person better etc. I like taking space now and then but at first it was a weird scary concept
His emotions are high, he's trying to process a lot and decompress. Sometimes it's easier to think logically about something when you're not actively in the situation. Space can be good if the person is mature. It can be bad if they are impulsive and immature.